Accelerometer Module for Use With A Touch Sensitive Device

ABSTRACT

An accelerometer module for use with a touch sensor on a device, a method of detecting acceleration using a touch sensor, and a computer program product for receiving the touch sensor data and producing output representative of acceleration. The accelerometer module provides a device with a touch sensor, such as a mobile phone, with the ability to sense acceleration, orientation, or both. The accelerometer module may sense acceleration along a single axis or multiple axis. Sensing acceleration along three axis may be useful for producing a handheld game controller or for providing input to many other applications. The accelerometer module applies a force against a deformable member to change the contact area between the deformable member and the touch sensor, wherein the contact area is a function of the amount of applied acceleration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the use of touch pads and touchscreens.

2. Description of the Related Art

An accelerometer is a device for measuring acceleration. Acceleration isthe sum total of external forces acting on an object divided by themass. Accelerometers are perhaps the simplest Micro Electro-MechanicalSystem (MEMS) device possible, sometimes consisting of little more thana suspended cantilevered beam or proof mass with some type of deflectionsensing and circuitry.

Accelerometers can be used to measure vibration on cars, machines,buildings, process control systems and safety installations. They canalso be used to measure seismic activity, inclination, machinevibration, dynamic distance and speed with or without the influence ofgravity. Applications for accelerometers that measure gravity, whereinan accelerometer is specifically configured for use in gravimetry, arecalled gravimeters.

Accelerometers are being incorporated into more and more personalelectronic devices such as media players and handheld gaming devices. Inparticular, more and more smartphones (such as Apple's iPhone) areincorporating accelerometers for step counters, user interface control,and switching between portrait and landscape modes.

Accelerometers are used along with gyroscopes in inertial guidancesystems, as well as in many other scientific and engineering systems.One of the most common uses for MEMS accelerometers is in airbagdeployment systems for modern automobiles. In this case theaccelerometers are used to detect the rapid negative acceleration of thevehicle to determine when a collision has occurred and the severity ofthe collision.

Although accelerometers have found widespread acceptance and utility,the functionality of the accelerometer must be designed and manufacturedinto the original equipment. There is no existing solution that allowsaccelerometer functionality to be added an existing electronic device.It would be desirable to have a module that would provide an existingelectronic device with the ability of sensing acceleration. It would beeven more desirable if the module was simple, quick to install, andcompatible with common portable electronic devices.

SUMMARY OF THE INVENTION

One embodiment of the invention provides an apparatus for sensingacceleration. The apparatus comprises a mobile electronic device havinga touch sensitive device, such as a touch pad or touch screen, thatprovides input to a processor, and a module selectively securable to themobile electronic device adjacent the touch sensitive device. The moduleincludes one or more acceleration-responsive mechanisms, wherein eachacceleration-responsive mechanism has a deformable member that contactsthe touch screen over a contact area that varies in response toacceleration. Optionally, the module may include threeacceleration-responsive mechanisms, wherein each acceleration-responsivemechanism detects acceleration in a different axis of a Cartesiancoordinate system. The deformable member is made of material that can besensed by the touch device.

Another embodiment of the invention provides a method of sensingacceleration. The method comprises disposing a deformable memberadjacent a touch sensitive device surface, directing a force ofacceleration to push the deformable member against the touch sensitivedevice surface to cause elastic deformation of the deformable member,and sensing a change in the contact area between the deformable memberand the touch sensitive device as a result of the elastic deformation.

A further embodiment of the invention provides a computer programproduct embodied on a computer readable medium and providing computerusable instructions for sensing acceleration. The computer programproduct comprises instructions for detecting a change in the contactarea of a first touch sensitive device region associated withacceleration along a first coordinate axis, instructions for detecting achange in the contact area of a second touch sensitive device regionassociated with acceleration along a second coordinate axis,instructions for detecting a change in the contact area of a third touchsensitive device region associated with acceleration along a thirdcoordinate axis, and instructions for determining an overallacceleration as the combination of the acceleration along the firstcoordinate axis, acceleration along a second coordinate axis, andacceleration along a third coordinate axis.

Other embodiments, aspects, and advantages of the invention will beapparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a mobile phone having a touch screen.

FIG. 2 is a block diagram showing the components of the mobile phone.

FIG. 3 is plan view of a mobile phone touch screen in accelerometermode.

FIG. 4 is a perspective view of an accelerometer module being coupled tothe mobile phone.

FIG. 5 is a plan view of the accelerometer module coupled to the mobilephone.

FIG. 6 is a cross-sectional view of the accelerometer module coupled tothe mobile phone.

FIGS. 7A-B are partial cross-sectional views of a first mechanism formeasuring the force of acceleration in a “Z” direction with a deformableball in relaxed contact with the touch screen and deformed contact withthe touch screen, respectively.

FIGS. 8A-C are partial cross-sectional views of a second mechanism formeasuring acceleration in an “X” direction with a deformable ball inslightly deformed contact under a spring force, greatly deformedcontact, and in relaxed contact, respectively.

FIGS. 9A-D are side views of deformable members that would providedifferent relationships between acceleration and contact area.

FIG. 10 is a partial perspective view showing a spring that biases alever to prevent loose swinging of the lever and maintain contactbetween the deformable member and the touch screen.

FIGS. 11A-B are partial cross-sectional views showing potentialattachment of a deformable member to a lever.

FIGS. 12A-B are partial cross-sectional views of a third mechanism formeasuring the force of acceleration in a “Z” direction with a deformableball in relaxed contact with the touch screen and deformed contact withthe touch screen, respectively.

FIG. 12C is a partial cross-sectional view of a fourth mechanism formeasuring the force of acceleration in a “Y” direction with a deformableball in relaxed contact with the touch screen. This mechanism utilizesfluid to convert motion in the “Y” direction to that in the “Z”direction to enable it to be sensed.

FIGS. 13A-B provide a flow diagram of a method for detectingacceleration of the accelerometer module.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

One embodiment of the invention provides an accelerometer module for usewith a touch sensitive device, such as a touch pad or touch screen, on amobile device. The accelerometer module may be used to provide a mobiledevice having a touch sensitive device with the ability to senseacceleration, orientation, or both. The accelerometer module cooperateswith the touch sensitive device to enable the mobile device to senseacceleration along a single axis or dual axis may be useful, forexample, for producing a pedometer, automotive vibration sensor, ortheft detection device. An accelerometer module that enables the deviceto sense acceleration along three axis may be useful, for example, forproducing a handheld game controller or three-dimensional graphicsinstrument. A mobile device with the capabilities of an accelerometermay be adapted to many other applications.

Another embodiment of the invention provides a method of detectingacceleration of an accelerometer module in cooperation with a touchdevice. The accelerometer module applies a force against a deformablemember to cause a change in the area of contact between the deformablemember and the touch sensitive device. The contact area is a function ofthe amount of the force applied against the deformable member.Monitoring the touch screen to determine the extent of changes in thecontact area of a deformable member enables the amount of the force tobe determined. Various mechanisms may be used to deform a deformablemember against the touch screen as a result of acceleration in variousdirections. For example, appropriate use of three independent mechanismscan enable the detection of acceleration along each of three axis.Electronic signals generated by the touch sensitive device may be usedseparately for various applications or combined to indicate an overallnet acceleration of the module.

Yet another embodiment of the invention is a computer readable mediumincluding a computer program product providing computer usableinstructions for carrying out a method of detecting acceleration. Thecomputer program product detects the contact area of each of one or moredeformable members and uses the detected area to indicate the amount offorce applied in a given direction. The amount of the force is generallyproportional to the increase in contact area in accordance with apredetermined function that may be empirically determined on the basisof the composition, shape and size of the deformable member. Thecomputer program product may determine the direction of the force inaccordance with a predetermined layout of the accelerometer module. Thepredetermined layout may establish that a particular axial component ofthe overall acceleration will be indicated by a force on the touchscreen in a particular region of the touch screen. Acceleration can thenbe determined from the force.

A touch sensitive device may be produced using various technologiesincluding, without limitation, a touch sensitive device selected fromthe group consisting of resistive, surface acoustic wave (SAW),capacitive, infrared, strain gauge, optical imaging, dispersive signaltechnology, acoustic pulse recognition, and frustrated total internalreflection. However, an embodiment including a capacitive touchsensitive device will be described in greater detail. A capacitive touchsensitive device is known to be capable of simultaneously detectingcontact at multiple points on the touch screen, whereas some touchsensitive device technologies are limited to detecting a single point ofcontact.

A capacitive touch sensitive device panel is coated with a material,typically indium tin oxide, that conducts a continuous electricalcurrent across the sensor. The sensor therefore exhibits a preciselycontrolled field of stored electrons in both the horizontal and verticalaxes and achieves capacitance. The human body is also an electricaldevice which has stored electrons and therefore also exhibitscapacitance. When the sensor's ‘normal’ capacitance field (its referencestate) is altered by another capacitance field, such as a finger,electronic circuits located at each corner of the panel measure theresultant ‘distortion’ in the sine wave characteristics of the referencefield and send the information about the event to the controller formathematical processing. Capacitive sensors can either be touched with abare finger or other conductive device, such as the deformable member.

Furthermore, a capacitive touch sensitive device can be made to sensethe area of touch as well as the location of the touch on the touchscreen. Higher touch pressure causes a finger tip to flatten more andcreates a larger tough area. In this manner, the touch sensitive devicecan determine the relative amount of pressure applied by a finger inproportion to the area touched. An embodiment of the invention includesa deformable member, such as a ball, having a conductive surface forcontacting the touch sensitive device in much the same manner as afinger. The deformable member is deformed under a force directed towardthe touch sensitive device by a weight that is being accelerated. Thedeformable member may be any three-dimensional shape that presents asurface at an angle to the touch sensitive device such that the contactarea between the surface and the touch sensitive device increases withincreasing force or acceleration. For example, the deformable member mayhave a generally rounded shape such as a sphere, spheroid, or ellipsoid;a shape having a generally rounded face directed toward the touchsensitive device; a generally pyramidal shape; a shape having one ormore generally inclined surfaces facing the touch sensitive device.Furthermore, it is not necessary for the deformable member to deformagainst the flat touch sensitive device surface over a round area.Rather, the deformation may be substantially linear along one or twoaxis.

The deformable member is disposed between the touch sensitive device anda mechanism for directing a force at the deformable member in adirection toward the touch sensitive device. In one embodiment, themechanism directs the force at a substantially perpendicular anglerelative to a planar touch sensitive device. The mechanism positions amass in a known relationship to the deformable member. Optionally, themechanism may be selected to direct a force that represents only asingle axial component of the overall acceleration.

A further embodiment includes multiple mechanisms that each direct aforce representing a different axial component of an overallacceleration. For example, a set of three mechanisms may be included,where each mechanism directs a force representative of one component ofa Cartesian coordinate system. The force measurements from each of thethree axis can be utilized separately or in combination to determine theoverall acceleration of the device.

A first type of mechanism may allow only forces directed perpendicularto the touch sensitive device (i.e., a “z direction”) to be appliedagainst the deformable member. Examples of such mechanisms include alever having a pivot axis and lever arm that are both substantiallyparallel to the plane of the touch screen, and a tubular slide extendingsubstantially perpendicular to the plane of the touch screen. A secondtype of mechanism may allow only forces directed in a first lateraldirection parallel to the touch screen (i.e., an “x direction”) to beapplied against the deformable member. Examples of such mechanismsinclude a right angle lever arm or a bell crank. If it is desired tomeasure a component of force in a third direction (i.e., a “ydirection”), then another of the second type of mechanism may bedisposed at a right angle to measure that force. Other types ofmechanisms may be utilized to measure the same or different forcecomponents.

The mechanism may be used in conjunction with a biasing member, such asa spring or elastic cord, which limits the range of motion of themechanism, maintains contact between the mechanism and the deformablemember, and maintains contact between the deformable member and thetouch screen. Furthermore, a biasing member may apply a sufficient forceto partially deform the deformable member, such that touch screen cansense when the force, and therefore the contact area, both increases anddecreases. Typically, the spring will have a first end coupled to thelever and a second end coupled to the structure. For example, a coilspring, tension spring, compression spring or wave spring may beutilized. See FIG. 10.

The deformable member must be secured in position between the mechanismand the touch sensitive device. Suitably, the deformable member may besecured to the mechanism, such as at the end of a lever facing the touchsensitive device. The lever is pivotally coupled to a structure andmaintains the position of the pivot point of the lever. A mass issecured to, or forms part of, the mechanism.

Each mechanism is secured to a structure that can be selectively coupledto the touch sensitive device or a device providing the touch sensitivedevice. The structure may, for example, take the form of a housing aframe. The structure may be suitably coupled to the touch sensitivedevice with a clip, or other fastener.

FIG. 1 is a plan view of a mobile phone 10 having a touch screen 12 andvarious conventional buttons 14. The touch screen 12 overlays a displaythat provides a graphical user interface. Depending upon the operatingsystem or software application that control the operation of the displayand touch screen, a number of icons are displayed to the user forselecting a desired operation. For example, a typical mobile phonedisplay will provide a signal strength indicator 16, battery chargegauge 18, calendar icon 20, text message icon 22, contacts directory 24,and a clock 26. A special icon 28 may also be provided to facilitateentering an accelerometer mode of operation.

FIG. 2 is a block diagram showing the components of the mobile phone 10.The mobile phone 10 includes components for user input to a processor30, such as a microphone 32, keypad 14 and touch screen 12. Userfeedback and information is generated by the processor 30 and providedto the user via a speaker 32 and display 34. The processor 30 has accessto a memory device 36 that enables storage and retrieval of data. Themobile phone communicates with a wireless telephone network via a radiosubsystem 38 coupled to an antenna 39. Note that the block diagram doesnot include many components or features known in existing mobile phones.Of course, mobile phone 10 could also include any component or featurethat is known in the art in addition to those shown within the scope ofthe preferred embodiments.

FIG. 3 is plan view of a mobile phone 10 having a touch screen 12 inaccelerometer mode. Certain high priority information has been moved tothe bottom of the touch screen 12, such as the signal strength indicator16, the battery charge gauge 18, contacts directory 24 and anaccelerometer mode exit button 40. An upper portion of the touch screen12 will be used in cooperation with an accelerometer module to becoupled to the phone 10. As shown, there are three predetermined regions42, 44, 46 of the touch screen 12 where a deformable member will bepositioned to indicate the X component, Y component and Z component of aforce, respectively. It is not necessary for these predetermined regionsto the displayed to the user, but these regions are shown for purpose ofillustration. Rather, this portion of the display might suitably displaya message, such as “Please attach accelerometer”, or an imageillustrating proper attachment of the accelerometer.

FIG. 4 is a perspective view of one embodiment of an accelerometermodule 50 being coupled to the mobile phone 10. This accelerometermodule forms a housing 52 that slides over the upper end of the mobilephone 10.

FIG. 5 is a plan view of the accelerometer module 50 coupled to themobile phone 10 in its operative position. As shown, the accelerometermodule 50 extends over the three predetermined regions 42, 44, 46 of thetouch screen 12. Separate subassemblies of the accelerometer module 50will cooperate with the predetermined regions 42, 44, 46, as describedfurther in reference to FIG. 6.

FIG. 6 is a cross-sectional view of the accelerometer module 50 coupledto the mobile phone 10. Optionally, the module 50 forms clips 52 thatfrictionally engage the perimeter of the mobile phone and secure themodule in position. The accelerometer module 50 positions threeaccelerometer mechanisms over the touch screen 12. Specifically, a firstaccelerometer mechanism 54 is positioned over the region 42 and sensesacceleration in the X direction, a second accelerometer mechanism 56 ispositioned over the region 46 and senses acceleration in the Zdirection, and a third accelerometer mechanism 58 is positioned over theregion 44 and senses acceleration in the Y direction. The operation ofthe individual mechanisms is described further below.

FIGS. 7A-B are partial cross-sectional views of a mechanism 56 formeasuring force in a “Z” direction (up and down on the page as shown)with a deformable ball 60. A fixed support bracket 62 extends from thewall and supports a proximal end of the lever 66. The proximal end ofthe lever 66 includes a pivot pin 64 and a distal end of the leversupports a mass 68. The lever 66 may be long enough that small upward ordownward movement the distal end of the lever 66 is nearly perpendicularto the plane of the touch screen 12. Moving the mobile phone 10 andaccelerometer module 50 in a “Y” direction (right and left on the pageas shown) or in an “X” direction (in and out of the page) will notinduce any deformation of the ball 60. Only movement that issubstantially vertical with respect to the touch screen will causedeformation of the ball 60. A coil spring 70 is disposed about the pivotaxis of the pivot pin 64 and has one leg that biases the lever towardthe touch screen by pushing a second leg against a tab on the supportbracket 62.

In FIG. 7A, the deformable ball 60 is in relaxed contact with region 46of the touch screen 12. The relaxed contact produces a contact areahaving a diameter D1. This contact area is sensed by the touch screen 12and provides the contact area associated with the region 46 to theprocessor.

In FIG. 7B, the deformable ball 60 is in deformed contact with the touchscreen as a result of vertical movement of the accelerometer module 50.The deformed ball produces a contact area having a diameter D2, whereindeformed diameter D2 (and the deformed contact area) is greater than therelaxed diameter D1 (and the relaxed contact area). The applicationprogram or operating system of the mobile phone receives thisinformation and uses the contact area as an indicator of an amount ofacceleration being applied in the vertical direction.

FIGS. 8A-C are partial cross-sectional views of a second mechanism 58for measuring force in a “Y” direction with a deformable ball 72 inslightly deformed contact with a different region 44 of the touch screen12 under the force of a spring 74 (FIG. 8A), greatly deformed contactcaused by movement of the module 50 to the right (FIG. 8B), and inrelaxed contact caused by movement of the module 50 to the left (FIG.8C), respectively. The second mechanism 58 includes a right-angled orL-shaped lever having a first leg 76 that extends substantiallyperpendicular to the plane of the touch screen to support a mass 78 anda second leg 80 that extends substantially parallel to the plane of thetouch screen. The L-shaped lever pivots about an axis that is parallelto the plane of the touch screen and aligned with the X-axis (in and outof the page). Accordingly, movement of the accelerometer module 50 inthe X-direction or the Z-direction will not induce any deformation ofthe ball 72.

In FIG. 8A, the ball is slightly deformed by the force of the spring 74to produce a contact area D3. In FIG. 8B, the module 50 is moved to theright resulting in further deformation of the ball 72 and producing alarger contact area D4. In FIG. 8C, the module 50 is moved to the leftresulting in less formation of the ball 72 and producing a smallercontact area D5. The application program or operating system of themobile phone receives this information and uses the contact area as anindicator of an amount of acceleration being applied in the Y-direction.Unlike the mechanism 56 of FIGS. 7A-B which could only detect onedirection of movement along an axis (i.e., upward movement in the +Zdirection), the mechanism 58 of FIGS. 8A-C provides sufficientinformation to sense movement two directions along an axis. Movement tothe right (i.e., in the +Y direction) causes a contact area that isgreater than the contact area when the accelerometer is stationary.Movement to the left (i.e., in the −Y direction) causes a contact areathat is less than the contact area when the accelerometer is stationary.The degree of movement or acceleration may be determined as well as thedirection, because the degree of increase or decrease in the contactarea in sensed by the touch screen and provided to the processor. Itshould be recognized that the first mechanism 56 may also be implementedto detect movement in two directions by increasing the force of thespring 70.

It should also be recognized that a third mechanism 54 (as shown in FIG.6) may be provided in the same manner as the second mechanism 58, exceptthat it is secured to the module at a right angle to the secondmechanism 58. Specifically, the third mechanism 54 has a pivot axis thatis parallel with the Y-axis such that it only senses movement in theX-direction. Furthermore, the third mechanism 54 makes contact with thetouch screen 12 in a different predetermined region 42 so that theprocessor can determine whether the force is attributable to the X, Y orZ axis.

FIGS. 9A-D are side views of deformable members that would providedifferent relationships between force and contact area, regardless ofthe type of mechanism or axial component of force being sensed. In FIG.9A, a triangular or pyramidal member 82 is mounted to a lever 83 andpresents a point or vertex onto the touch screen 12. The vertex would beexpected to initially produce a very small contact area and require lessforce to deform than a sphere. In FIG. 9B, a spherical section 84 iscoupled to a lever 85 and presents a spherical surface against the touchscreen 12. The spherical section 84 should produce a similarrelationship between force and contact area as a complete sphere, butwill require less space because it is thinner and will require lessangular displacement of the lever. In FIG. 9C, an irregularly shapedmember 86 is coupled to a lever 87 and illustrates that, for any givenmaterial, a profile may be modified to produce a desired relationshipbetween force and contact area. In FIG. 9D, a hollow member 88 iscoupled to a lever 89, where making the member hollow may result in agreater contact area during deformation since there is no internalmaterial to compress or stretch. Such a hollow member may be perforatedor air tight.

FIG. 10 is a partial perspective view of the first mechanism 56 with acoil spring 70 that biases the lever 66 toward the touch screen 12 toprevent loose swinging of the lever and maintain contact between thedeformable member 60 and the touch screen 12. As previously discussed,embodiments of the spring 70 may partially deform the member 60 toenable detection of both upward movement via increases in contact areaand downward movements via decreases in contact area. The coil spring 70will typically have one or more turns or coils and two legs that projectoutward to engage the lever 66 and the support bracket 62, such asagainst a tab 63.

FIGS. 11A-B are partial cross-sectional views showing potentialattachment of a deformable member to a lever. In FIG. 11A, a deformablemember 90 takes the shape of a hollow sphere and is coupled to the lever92 by a rivet or other fastener 94. In FIG. 11B, a spherical section 96includes tabs 98 for coupling to the lever with rivets or otherfasteners 94. It should also be recognized that the deformable membersmay be secured using adhesives or other attachment means.

FIGS. 12A-C are partial cross-sectional views of embodiments using atubular or cylindrical chamber to hold the deformable member, mass, andspring in a manner so that acceleration in a particular direction causesdeformation against the touch sensitive device. In FIG. 12A, the module50 includes a mechanism 140 forming a tubular chamber defined by walls142. The chamber walls 142 secure the deformable member 60, the mass 68,and a spring 144 in alignment. Accordingly, acceleration of the modulein the +Z direction (upward on the page) will cause deformation of themember 60 against the touch screen 12, as shown in FIG. 12B. As in otherembodiments, the spring may simply secure the mass 68 against thedeformable member 60 such that deformation indicates acceleration in the+Z direction, or the spring may normally cause a first degree ofdeformation in order to indicate acceleration in the +Z direction by anincrease in deformation and indicate acceleration in the −Z direction bya decrease in deformation.

FIG. 12C is a partial cross-sectional view of an embodiment fordetecting acceleration in the +Y or −Y direction (as shown) or even inthe +X or −X direction by orienting the mechanism at 90 degrees. Whereasthe mechanisms of FIGS. 8A-C use a pivot to convert a force parallel tothe touch sensitive device to a force perpendicular to the touchsensitive device, this mechanism 150 uses a fluid in the tubular chamberto enable the direction of the force to be changed as desired.Accordingly, acceleration of the module 50 in the +Y direction (to theright of the page) causes a high mass hydraulic piston 152 to move tothe left, pushing the fluid 154 against the low mass piston 156, whichin turn deforms the member 60 against the touch screen 12. The hydraulictube is bent 90 degrees so that movement of the higher mass piston 152in a direction parallel to the plane of the touch sensitive device 12 isconverted to movement of the low mass piston 156 perpendicular to thetouch sensitive device 12. Optionally, the low mass piston could bereplaced with a membrane or bellows to cover the end of the tube 158 andcontain the fluid 154. Hydraulic pressure would deform the membrane orbellows. This would enable the membrane or bellows to also function asthe deformable member 60. Again, the spring may be used to deform themember 60 so that acceleration in both the +Y and −Y direction (or boththe +X and −X direction) can be detected by sensing an increase ordecrease in deformation.

FIGS. 13A-B provide a flow diagram of a method 100 for detectingaccelerations that are applied to the accelerometer module. The user mayselect to enter an accelerometer mode of operation on a touch screendevice (step 102), such as by pressing an accelerometer mode icon. Whenthe accelerometer module is physically installed, the touch screendetects contact in certain predetermined regions to indicate that anaccelerometer module has been properly coupled relative to the touchscreen (step 104). During use of the accelerometer, the method monitorsthe contact area of the deformable member associated with each of threecomponents of acceleration in a Cartesian coordinate system (step 106).

If a change is detected in the contact area associate with the “X” axis(step 108), then it is determined whether the contact area increased ordecreased (step 110). If the contact area increased, then there is anindication of an acceleration in the positive X direction (+X) in anamount that is proportional to the extent of increase in the contactarea (step 112). However, if the contact area decreased, then there isan indication of an acceleration in the negative X direction (−X) in anamount that is proportional to the extent of decrease in the contactarea (step 114). The function of this proportionality may be stored inthe application software.

If a change is detected in the contact area associate with the “Y” axis(step 118), then it is determined whether the contact area increased ordecreased (step 120). If the contact area increased, then there is anindication of an acceleration in the positive Y direction (+Y) in anamount that is proportional to the extent of increase in the contactarea (step 122). However, if the contact area decreased, then there isan indication of an acceleration in the negative Y direction (−Y) in anamount that is proportional to the extent of decrease in the contactarea (step 124). The function of this proportionality may be stored inthe application software.

Furthermore, if a change is detected in the contact area associate withthe “Z” axis (step 128), then it is determined whether the contact areaincreased or decreased (step 130). If the contact area increased, thenthere is an indication of an acceleration in the positive Z direction(+Z) in an amount that is proportional to the extent of increase in thecontact area (step 132). However, if the contact area decreased, thenthere is an indication of an acceleration in the negative Z direction(−Z) in an amount that is proportional to the extent of decrease in thecontact area (step 134). The function of this proportionality may bestored in the application software.

Having detected whether there was any acceleration in the X, Y or Zdirections, and having determined the extent of the acceleration wheredetected, the method provides the resulting X, Y and Z components ofacceleration to an application program for further use (step 136). Ifthe user wants to exit the accelerometer mode (step 138), then theprocess ends. Otherwise, the method continues in the accelerometer modeand returns to step 106 to continue monitoring the contact areas on thetouch screen. Application programs, such as pedometers or video games,may use the output of the method in a wide variety of ways.

The terms “comprising,” “including,” and “having,” as used in the claimsand specification herein, shall be considered as indicating an opengroup that may include other elements not specified. The terms “a,”“an,” and the singular forms of words shall be taken to include theplural form of the same words, such that the terms mean that one or moreof something is provided. The term “one” or “single” may be used toindicate that one and only one of something is intended. Similarly,other specific integer values, such as “two,” may be used when aspecific number of things is intended. The terms “preferably,”“preferred,” “prefer,” “optionally,” “may,” and similar terms are usedto indicate that an item, condition or step being referred to is anoptional (not required) feature of the invention.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. An apparatus for sensing acceleration, comprising: an electronicdevice having a touch sensor input to a processor; and a moduleselectively securable to the electronic device adjacent the touchsensor, the module including one or more acceleration-responsivemechanisms, each acceleration-responsive mechanism including adeformable member that contacts the touch sensor over a contact areathat varies in response to acceleration.
 2. The apparatus of claim 1,wherein the module includes three acceleration-responsive mechanisms,wherein each acceleration-responsive mechanism detects acceleration in adifferent axis of a Cartesian coordinate system.
 3. The apparatus ofclaim 1, wherein each acceleration-responsive mechanism comprises alever pivotally coupled to the module.
 4. The apparatus of claim 3,wherein the lever is an L-shaped lever.
 5. The apparatus of claim 3,wherein each acceleration-responsive mechanism further comprises abiasing member disposed to bias the lever toward the touch screen. 6.The apparatus of claim 1, wherein the touch screen is a capacitive touchscreen.
 7. The apparatus of claim 1, wherein eachacceleration-responsive mechanism includes a mass mounted to deform thedeformable member only in response to acceleration along a single axis.8. A method of sensing acceleration, comprising: disposing a deformablemember adjacent a touch sensor surface; directing an acceleration topush the deformable member against the touch sensor surface to cause achange in the degree of elastic deformation of the deformable member;and sensing a change in the contact area between the deformable memberand the touch sensor as a result of the change in the degree of elasticdeformation.
 9. The method of claim 8, further comprising: applying asubstantially constant biasing force to push the deformable memberagainst the touch screen surface to cause a first extent of elasticdeformation of the deformable member; and directing an acceleration tooppose the substantially constant biasing force and result in a secondextent of elastic deformation of the deformable member that is less thanthe first extent of elastic deformation.
 10. The method of claim 9,further comprising: physically limiting the acceleration that isdirected to push the deformable member against the touch screen to be anacceleration along a defined axis; and identifying the direction of theacceleration along the defined axis by determining whether the contactarea increased or decreased.
 11. The method of claim 10, furthercomprising: identifying the relative magnitude of the acceleration bydetermining the extent of the change in the contact area.
 12. The methodof claim 11, wherein the step of identifying the relative magnitude ofthe acceleration by determining the extent of the change in the contactarea, includes using a correlation between contact area andacceleration.
 13. The method of claim 12, further comprising: combiningthe direction and relative magnitude of the acceleration along each ofthree coordinate axis in order to determine the direction and relativemagnitude of an overall acceleration.
 14. A computer program productembodied on a computer readable medium and providing computer usableinstructions for sensing acceleration, comprising: instructions fordetecting a change in the contact area of a first touch sensor regionassociated with acceleration along a first coordinate axis; instructionsfor detecting a change in the contact area of a second touch sensorregion associated with acceleration along a second coordinate axis;instructions for detecting a change in the contact area of a third touchsensor region associated with acceleration along a third coordinateaxis; and instructions for determining an overall acceleration as thecombination of the acceleration along the first coordinate axis,acceleration along a second coordinate axis, and acceleration along athird coordinate axis.
 15. The computer program product of claim 14,wherein the instructions for determining an overall acceleration includeinstructions for combining the acceleration along the first coordinateaxis, acceleration along a second coordinate axis, and accelerationalong a third coordinate axis as vectors having both a direction and amagnitude.